The present invention relates to the general field of systems for injecting fuel into a combustion chamber in a turbomachine. It relates more particularly to fuel pump means fitted to such injection systems.
As shown diagrammatically in FIG. 5, a system for injecting fuel into a turbomachine typically comprises: a pump 102, e.g. a gear pump, driven by a motor (not shown) enabling fuel to be taken from a fuel tank 104; a plurality of injectors 106 placed in a combustion chamber of the turbomachine and each provided with a fuel metering valve 108; and a fuel metering device 110 interposed between these two sets of elements in order to control the rate at which fuel is to flow from the pump to the injectors. The excess fuel coming from the metering device 110 is reinjected to the inlet of the pump 102.
With such a configuration, the rate at which fuel is injected into the combustion chamber of the turbomachine depends in particular on the setting of each injector 106, on the coking which forms on the nose of each injector, and on the differences in height between the injectors inside the combustion chamber. Furthermore, friction between the metering valve 108 of each injector 106 and a bushing in which it slides gives rise to hysteresis phenomena causing the metering valves to open and close after a delay. As a result fuel injection into the combustion chamber is non-uniform, and that can give rise in particular to difficulties in lighting the turbomachine.